The invention relates to a mobile high voltage network to supply an electrical consumer unit connected by a plug-in connector and which can be actuated by means of mechanical switches, with a fuse responding in the event of a short-circuit.
So far, few applications have been known for the mobile use of electrical networks of high power transmission. Basically, the conditions and solutions which have become known from stationary high voltage networks have been taken as the basis for this. With such networks, for which only alternating voltages are customary, cable breakage and the separating of connection couplings under load on account of the zero passage of the voltage gradient cause no problems. With a view to the greatest possible flexibility, a high degree of efficiency, a low expenditure on components, as well as a reasonably priced solution, including the expenditure on power electronics, the loss through the power electronics, as well as the expenditure for the stabilization of the network frequency and the network voltage, it has thus far been uneconomic for power transmission by means of high voltage networks based on alternating or direct current.
In the mobile field, electronically controlled and monitored technical devices have become known already which are capable of self-diagnostic checking. That means that during operation, faults which occur are detected and appropriate actions are instigated.
The task of the invention lies in creating a mobile high voltage network of the type described in the introduction hereto, that is economic to operate and to monitor.
This task is solved by the fact that the mobile high voltage network carries a direct voltage, and a separate diagnostic and protection monitoring system is assigned to each electrical consumer unit or load. Such a mobile high voltage network, in conjunction with the diagnostic and protection monitoring makes it possible, before the starting up of any consumer circuit, to carry out the protective monitoring so as to ensure that all the components are fully operational. Without this self-diagnostic check with proof of the capacity to operate, the relevant consumer circuit is not connected.
The diagnostic and protective monitoring device detects insulation faults and faults of the electrical connection. The diagnostic and protective monitoring device also prevents any separation of the electrical connector when live. In the event of too high electrical current, a fuse prevents the overloading of the diagnostic and protective monitoring device and the electrical line connections and junctions.
The diagnostic and protection monitoring is, however, also used to regulate the switching off of the consumer so that the network connection can be separated. For this, the consumer is disconnected from the high voltage network and the remaining network circuits are monitored to see if they are live. In particular, consumers with stored energy—electrical accumulators or also machines, which on stopping still feed current into the consumer—are transferred via a short-circuit connection into the safe condition with no voltage and no current. As soon as the consumer has definitely reached the condition where there is no voltage, the protection monitoring releases the plug-in connection for the separation.
This allows a separation of components carrying D.C. voltage, without the surrounding medium being ionized and without any arc occurring. The current can therefore be safely interrupted. In this way, no special protection medium, (e.g. hydrogen) is needed in the contact area and devices to blow out arcs. The operational reliability is increased many times more that with so far customary devices which use protection gas and arc blow-devices. The occurrence of an arc is excluded by the proposed solution. There is, therefore, no burning off of the contacts, nor is any device needed to extinguish arcs. Over the whole lifespan, without any additional measures the operational reliability of the diagnostic and monitoring, protection is therefore guaranteed. Through the monitoring of insulation faults, line breakage, or too great a flow of power, it is guaranteed that no danger arises when using electronically operated machines through the high voltage network.
The parallel circuit of a mechanical switch and a power switch makes it possible to use the advantageous properties and characteristics of these components to the base advantage. Thus, electronic power switches are in a position to by-pass relatively large potential differences with arc formation, whilst mechanical switches are very prone to this.
On the other hand, electronic power switches, unlike mechanical switches, exhibit high losses. When following the stated method of switching both when switching on and switching off the consumer, due to the effective electronic power switches, on the mechanical switch, there is a very slight voltage difference, which cannot adequately ionize the environment so as to cause no arcs. In addition, with the consumer switched on, only a slight drop in power is detected at the switches. The degree of effectiveness of the switching device is higher, and the thermal incidence, which is slight on account of the reduces loss of power, can be dissipated to the environment without additional cooling devices.
The features of the invention bring about on the mechanical switches certain preset voltage levels, which make it possible to establish the proper function of the switches. In addition, the current path takes over the dissipation of the slight leakage current of the power switches, in order to definitely exclude burning off on the contacts.
Due to the features of the invention, the plug-in connector cannot be separated when it is under electrical voltage. Therefore, any danger from the occurrence of an arc or contact with live components is excluded. Only in the state where there is no current and no voltage can the connector be disconnected.
The features of the invention make it possible for the diagnostic device to detect potential changes on the screening line, which occur in the event of damage in the insulation fitted between the line carrying current and the protection line through external effects or the interruption of the screening line. The network is then reliably switched off, so that there can be no danger from any damaged line. It is, therefore, guaranteed that the essentially higher probability of the occurrence of harmful effects on the lines in mobile use is not faced with a higher danger potential.
The features of the invention ensure the detection of insulation faults or line interruptions of lines from both the positive and negative pins.
Further advantageous details and features of the invention can be seen in the claims.
The invention is explained in greater detail hereinafter by reference to the drawings.